Study On The Variable Characteristic Of The Water Stable Isotopic Compositions In Yangtze River Basin

Isotope technique is a very important tool to explore the mechanism of water cycle in large river basin, and to identify the effects for climate change and human activities on river water. Study on isotope tracing in river is very important to modify watershed forecast modeling, and to find spatial-temporal distribution characteristics of water resources in large river basin. First, the thesis analyzes the precipitation isotopic abundance in the mainland of China especially in the Yangtze River basin based on the IAEA GNIP database, and computes the continental effect, altitude effect, and temperature effect, as well as precipitation amount effect, respectively. According to calculation results, one or two effects mentioned above on meteoric precipitation abundance whereas unremarkable precipitation amount and temperature effects are founded. Because some tributaries of the river originate from the places where precipitation isotope is obvious high what may affect the isotope abundance of the mainstream of the river. In terms of meteoric precipitation analysis, the criteria for a network to monitor isotope compositions of runoff in Yangtze were designed. The first water isotopic campaign and regular 4-station water sampled at Jan-2003 and Oct-2003, respectively. The temporal and spatial variations of river water isotope along the main stem were analyzed. New water body from tributaries coming to the main stem of Yangtze is one of the main reasons of spatial isotopic variations. The results revealed that temporal and spatial variations in the hydrogen and oxygen-isotope of water samples along the main stem of Yangtze strongly rely on the isotope pattern of the regional precipitation. Furthermore, signatures derived from influx of evaporatively enriched waters through the several reservoirs or lakes along the system will be resulted in d-excess values increasing. The peak of the river water isotopic temporal variations is good corresponding to the boundary point of the beginning or ending for annual flooding period at site.